Recently, in the field of endoscope, a swallowable capsule endoscope has been proposed. The capsule endoscope is provided with an imaging function and a radio communication function. This capsule endoscope has a function of moving in a body cavity, for example, internal organs such as stomach and small intestine with peristalsis thereof, during a period after it is swallowed from a mouth of the subject for observation (examination) until it is naturally discharged from the subject, and imaging intra-subject images, for example, at an interval of 0.5 second with the movement thereof.
While the endoscope is moving in the body cavity, image data imaged in the body by the capsule endoscope is sequentially transmitted to the outside by radio communications, and stored in a memory provided in an external device. If the subject carries a receiving device having the radio communication function and the memory function, the subject swallows the capsule endoscope and then can freely move until the endoscope is discharged. After the capsule endoscope is discharged, a doctor or a nurse can perform diagnosis by displaying the images of the internal organs based on the image data stored in the memory (see, for example, Patent Document 1).    Patent Document 1: Japanese Patent Application Laid-open No. 2003-19111